1. Field of the Invention
This invention generally relates to a system for evaluation of the metal corrosion preventiveness of coolants. More particularly, this invention relates to a system for "instantaneous" evaluation of the metal corrosion preventiveness of a coolant currently used generally in an internal-combustion engine system, providing an instant judgment whether it is proper or not to continuously use the coolant.
2. Description of the Prior Art
Generally, a coolant being used in an internal-combustion engine system includes a coolant composition available on the market and proportionally abundant diluting water. The coolant generally includes a metal corrosion preventive agent to provide the coolant with a metal corrosion preventive property for prevention of corrosion of the metal parts of the cooling system of the internal-combustion engine system.
The corrosion preventiveness of a coolant under use in an internal-combustion engine system, however, gets gradually deteriorated or degraded with time due mainly to the heat from the engine and occasional water supplement. The coolant with such degraded corrosion preventiveness will no longer provide adequate metal corrosion prevention and will eventually even promote corrosion of the metal portions of the cooling system of the internal-combustion engine system. In such a case, immediate change with a fresh coolant is recommended.
When the coolant in the cooling system of an internal-combustion engine system looks or is presumably judged no longer providing effective metal corrosion prevention or even promoting metal corrosion, it is generally time for the coolant to be wholly replaced with a fresh coolant containing a fresh corrosion preventive agent. Usually the time for such replacement is simply decided by the period of actual use of the coolant in a cooling system or by individual users' preferences, which naturally varies widely depending on individual users.
Such replacement or change of coolants in accordance with the duration of actual use of a coolant in an internal-combustion engine system or individuals' preferences is often inappropriate (inadequately late or unnecessarily soon) since the working condition of the coolant is subject to various factors of use of the engine system or the coolant. In addition, the time of such change is also subject to the components and/or quality of coolants as individual coolants can include different coolant compositions. Occasionally the coolant under use in a cooling system is changed with a fresh coolant too late and the corrosion of some metal parts in the cooling system may have already started. Occasionally the replacement of the coolant in a cooling system with a fresh coolant is unnecessarily too soon.
A coolant testing conventionally practiced for evaluation of the metal corrosion preventiveness of coolants after considerable use comprises an indirect evaluation of the metal corrosion preventiveness of coolants by studying the conditions of various elements of the coolants such as the concentration of the contained ethylene glycol, pH values and the concentration of various metal ions liberated in the coolants as well as the concentration of the other metal corrosion preventive agents.
Another coolant testing conventionally practiced for evaluation of the metal corrosion preventiveness of coolants after considerable use comprises a direct evaluation of the metal corrosion preventiveness of the coolants by directly studying the corrosion of various metal samples by submerging in the coolants under predetermined conditions.
Such an indirect evaluation of the corrosion preventiveness of coolants, however, will not always provide reliable judgment on the workability of the coolants tested due to the lack of reliable criteria for judgment. Without reliable criteria for judgment, it is not possible to precisely determine whether the coolant tested is proper or not to be continuously used. Further, the data obtained from such an indirect evaluation test fluctuate excessively depending on the constitution or components of coolants, making such judgment virtually impractical. In addition, each such measurement requires an extensive and expensive measurement system which can only be utilized in a research facility.
On the other hand, such a direct evaluation of the metal corrosion preventiveness of coolants also requires a special testing system which can only be used in a research facility, thus incapable of providing an instantaneous evaluation.
Neither of such testing methods can be easily or practically performed by individual users on the spot to determine whether the coolant in the cooling system of their cars, for instance, can be continuously used for some more time or should be replaced immediately before the metal portions of the cooling system start to get corroded.
Japanese Patent Publication No. 63-19815 (U.S. patent application 866074, Dec. 30, 1977, Assignee: Texas Instruments Incorporated) discloses a simple testing apparatus for coolant corrosion preventiveness. This apparatus comprises a silver reference electrode and a sensor or working electrode comprising steel and aluminum. The corrosion preventiveness of coolants is indirectly studied from the redox potential to be chemically generated between the two electrodes placed in the coolant tested.
The reliability of the above apparatus at first may be considerable, however, the reliability is destined to deteriorate with time and after repeated use of the electrodes of the apparatus as the electrodes themselves eventually get corroded, eventually providing metal corrosive evaluation data which are no longer reliable or off the true evaluation values. Because of this intrinsic defect, the above coolant evaluation apparatus will wrongly judge that a still usable coolant should be replaced immediately.
There has long been felt a need by users, mechanics and servicemen as well as dealers of coolant compositions or metal corrosion preventives for a reliable and handy as well as quick test system for evaluation of the metal corrosion preventiveness of coolants which can be used for a long duration of time without losing its reliability.
Accordingly, it is an object of the present invention to provide an evaluation test system for quickly, accurately and handily evaluating the metal corrosion preventiveness of coolants being used in cooling systems generally of internal-combustion engine systems.
It is another object of the present invention to provide an evaluation test system for reliably evaluating over a long duration of time the metal corrosion preventiveness of coolants being used generally in internal-combustion engine systems.